A conventional boiling water reactor includes a plurality of control rod drives (CRDs) mounted to a reactor pressure vessel, each of which includes an output rod extending therefrom for selectively inserting and withdrawing conventional control rods into and out of a conventional reactor core for controlling reactivity thereof.
The CRDs include many components and are initially assembled in a manufacturing plant and then installed into the reactor pressure vessel. During operation of the reactor, the CRDs are subject to nuclear radiation and become contaminated. Routine maintenance of the CRDs requires disassembly thereof, and since the CRDs have been contaminated, maintenance personnel must wear suitable protective clothing including, for example, plastic hoods, and triple gloves which decrease visibility and dexterity for performing the maintenance operation.
In one CRD design, the CRD includes a housing endcap which has an outer diameter slightly less than the inner diameter of a complementary mounting receptacle of the housing in which it is inserted. This tight clearance between the endcap and the housing receptacle results in cocking of the endcap during disassembly of the endcap from the housing if the endcap is not uniformly withdrawn from the receptacle. The cocking of the endcap in the receptacle will cause the endcap to bind and therefore prevent its disassembly therefrom. Since the CRD has been contaminated due to operation in the reactor pressure vessel, the protective clothing worn by the maintenance personnel increases the difficulty in removing the endcap without cocking and resulting binding thereof.